Posted by: Prospector PJ18 MAR 2014
A crystal discovered in the Jacks Hills region of Western Australia has been found to be 4.4 billion years old. Its analysis suggests that the earth could have supported life 4.3 billion years ago — almost a billion years before the oldest fossil records.
The zircon crystal is the oldest piece of the planet ever discovered and suggests that the earth’s crust appeared just 100 million years after the earth itself was formed as a ball of molten rock, 4.5 billion years ago. It also dates the earth’s crust at just 160 million years after the solar system itself was formed.
The age of the crystal, which measures just 200 by 400 microns — about twice the diameter of a human hair — was determined using a method based on the radioactive decay of uranium to lead. Atom-probe tomography identified individual atoms of lead in the crystal and measured their mass.
These findings support the notion that the early earth was cooler than previously thought, and able to support oceans and possibly life. This period is known as the Hadean eon, after Hades, the Greek god of the underworld, because of the “hellish” conditions, which would at first have included a molten surface and meteorite bombardment.
Despite these mind-boggling numbers, the earth is still relatively young in universal terms. The universe itself is thought to be about 13.8 billion years old, with its date of birth occurring at the time of the Big Bang. Measurements of cosmic background radiation give the cooling time of the universe since the Big Bang, and measurements of the expansion rate of the universe can be used to calculate its approximate age by extrapolating backwards.